Overall Aims 1. To examine basic technical and methodical issues involved in PET and fMR imaging of cognitive function. 2. To apply multiple injection [150]water PET and fMRI protocols in order to map systems involved in cognitive operations or functions such as timing, planning, sequencing, attention, language, emotion, and memory. 3. To apply them to the study of cognition in healthy normal individuals. 4. To apply them in order to explore disturbances in cognitive function that occur in mental illnesses that are hypothesized to have neurodevelopmental origins (i.e., schizophrenia and autism), as well as disturbances in cognitive function that result from focal vascular lesions. 5. To use them to explore disturbances in cognitive function resulting from acute and chronic use of addictive, psychoactive substances such as nicotine, marijuana and alcohol.